Yep, your calculation is correct. You probably have to feed additional power somewhere in the middle of this string. I have 10 meters but with less LEDs, my consumption is about 5A. I have to feed in at two points else not all LEDs get enough current to show full brightness. 40A need quite a bit of a wire, the internal are not suited for such amounts.

Well when you say series rather than parrallel then your drawing 1.2 amps but at 165 voltswhich isn't that bad if you get/build a hv supply than with regular diodes and a few caps that can handle the voltage you can power them all nicely right from the mains ac(once rectified and filtered it comes out to 167ish volts), althouth I don't know how the results would be in series with those strips since there already in series/parrallelThis would help as I doubt you have 8 or 6 gauge wire in those strips to handle that 40 amps

You do attach them serially but the power consumption is parallel because the strip contains the controlling chips, you just have to supply enough current and control the chips with a special kind of shift register.

If you're sure that never 100% of the LEDs are at full power you can go for the 20A power supply. 4 supply points are probably not enough. I'd go for at least 10 supply points giving 2A each which is probably more than enough for the flexible printed connections on the strip. I have real wires between my LED elements and with 2A per supply point the wires get remarkably warm but not hot.